Mr Clarkson, who lived with Smith, climbed out of a window yelling: “There’s kids upstairs, get the kids.”

Another neighbour, Mike Dykes, spotted the accused sitting opposite the burning home with a blanket wrapped around her.

The court heard when Mr Clarkson asked Smith how many ­children were inside the inferno, she snapped back: “How the f*** do I know?. She has everyone up there.”

Scene: The fire damage at the flats in Prestatyn (Image: PA)

Prosecutor Ian Murphy QC told jurors: “The prosecution say the fire was deliberately started by the defendant who had been drinking heavily that day and who, over a period of about two months leading up to October 19, had demonstrated anger and hostility towards Lee Anna and also ­jealousy of her.

“It is the prosecution case that on a number of occasions the defendant made threats to or about Lee Anna that she would ‘see your house on fire with you and your kids in it’.”

Liam and Charlie were rescued from the blaze at Prestatyn, North Wales but died later in hospital.

McDonald’s worker Liam managed to speak to paramedics at the scene, despite his horrific burns. He begged: “The babies, are the babies okay?”

The court heard he also said: “It was Mel. She said, ‘I’m going to burn the house down.’ She was shouting through the letterbox.”

When police later spoke to Smith, she denied any ­involvement.

She told officers: “One minute I was sitting in the lounge and the next I saw smoke coming from underneath the flat door, so I went to the bedroom and woke up my flatmate told him there was a fire and we climbed out the bedroom window.

“I hurt my arm while climbing.”

Harrowing: Fire crews at the scene (Image: PA)

Mr Murphy told the court: “The ­prosecution submit this is a significant lie and an attempt to portray herself as a victim rather than the perpetrator of the fire.”

On the day of the killings, jurors, were told, landlord Jay Liptrot called to the property to be met with a tirade from Smith about Lee Anna.

She allegedly described her as a “scruffy, dirty bitch”.

Hours later, she told a barmaid at her local pub she “hated the girl”, Mold crown court heard.

Along with five counts of murder, the 43-year-old is also accused of threatening to burn down the home of Samantha Schofield, who she claimed had an affair with Mr Clarkson.

She told Samantha’s sister Amy she had almost set light to the house one night last August but was unable to carry out the attack as she was drunk, jurors heard.

The court was told Mr ­Clarkson’s car was also vandalised. The windscreen wipers were bent and wing mirrors kicked.

Pink milkshake had been thrown at the vehicle and around 20 matches were recovered outside Smith’s front gates while a matchbox was found underneath the motor.